American Turtles' Surprising Habits Revealed

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The planet's second-largest population of loggerhead turtles — a
species that is endangered in many spots around the world —
frequents U.S. beaches, from North Carolina to the Gulf Coast of
Florida. And now a decadelong tracking study has revealed
surprising new information on the turtles' travels.

But it turns out loggerhead turtles are the dependable type — the
sort of turtle you'd want to bring home to Mom and Dad. Wild
thrill-seekers they are not, sticking to their usual
migration path time and time again.

Most of the turtles in the study rarely strayed from the United
States continental shelf, and traveled from nesting grounds along
the southeastern seaboard as far north as New Jersey to forage in
the summer, and as far south as Florida and the Bahamas in the
winter, and returned to the same areas within each region during
each season.

"North American
loggerhead sea turtles are really predictable — they don't do
the kooky stuff. They don't go wandering off very often," said
Lucy Hawkes, an ecologist at Bangor University in England.

So in an ironic twist, Hawkes said, it was precisely the lack of
surprising turtle behavior that was one of the biggest surprises
to come out of the research, which is helping to inform
conservation of U.S. loggerheads.

Between 1998 and 2008, researchers tracked the movements of 68
adult female loggerhead turtles, sometimes for more than two
years straight. (After they hatch and scamper into the sea, male
loggerheads never return to land, making them more difficult to
study.)

As the turtles buried their eggs in the sand on North Carolina
beaches, researchers epoxied satellite tags to their shells.
"It's not difficult, but it takes a bit of time," Hawkes told
OurAmazingPlanet. [Related Images:
Tagging and Tracking Sea Turtles ]

In a schedule that mirrors that of human snowbirds, most of the
animals head south for winter and north in the summertime.

"And they're quite good at predicting when to arrive," Hawkes
said. "They seem to arrive just as soon as the water is warm
enough and leave a week before it gets too cold."

Because they're cold-blooded animals, the turtles can get into
trouble if they end up in chilly waters — cool temperatures slow
down their metabolism, making the turtles sluggish and easier
targets for hungry predators.

However, fine-tuned as the turtles are to water temperature,
Hawkes said it's still not clear how the loggerheads come by
their inside information.

Linking the turtles' movements to temperature allows researchers
to pinpoint where the animals are with astounding accuracy, and
Hawkes said the findings have already proved useful.

Forecasting turtle moves

A U.S. Army Corps of Engineers project was scheduled to begin
dredging in the Delaware River, but the new data revealed the
area would be full of loggerheads at the time. Managers shifted
the start date to avoid affecting the turtles, Hawkes said, "so
we're really lucky we've been able to produce some real
conservation action on the ground."

Hawkes pointed to the change as an example of the comparative
advantage of the population's loyalty to U.S. waters. Since
satellite data revealed the turtles rarely leave U.S.
jurisdiction, only one country must deal with conservation
issues.

Such is not the case for loggerheads that live along the west
coast of Africa, where the home range can include coastlines of
eight or more countries.

And it's in this region of the world that the
turtles are facing many threats. Loggerheads, huge turtles
that weigh in at more than 250 pounds (113 kilograms), with
shells that span more than 3 feet (1 meter) from front to back,
are killed for meat; their eggs are taken and sold; in addition,
the turtles are killed for their blood. Some local traditional
medicine recommends a bath in loggerhead blood as a cure for
leprosy, Hawkes said.

The U.S. population of loggerhead turtles appears to be doing
fairly well. Estimates range from 30,000 to 50,000 adults. Add in
juveniles, and the number could be closer to 100,000.

"That sounds like a huge number, and it is," Hawkes said. "But
it's the world's second-largest population," she said, so it's a
large proportion of all the loggerhead turtles on Earth, making
their protection all the more important.